After breaking up with Jamie Burke a few months ago, Sienna Miller is back in the dating game with a new BF, Matthew Rhys of Brothers and Sisters. The couple met on the set of The Edge of Reason a while back and starting dating in June, at the urging of Keira Knightley, UK's Daily Mail reports. "This is the first bloke Sienna has been serious with since she finally split from Jude. These vicious allegations of her being with Sean 'Diddy' Combs and splitting up his relationship with Kim Porter are awful," a pal says. "But they have actually worked in her and Matthew's favor a bit. It has taken the heat off their relationship."

But just when we know about Sienna's summer love, is it over already? Rumors are popping up about Sienna possibly hooking up with Sean Bean, her much, much older co-star in A Woman of No Importance. "She is completely mesmerized by Bean already," an insider says. "She has told friends that she can't help feeling transfixed by his green eyes and loves the fact that he is a real macho man." Gross -- he's nearly twice her age and was married for the first time before she was even born!